Typically, nonionic synthetic detergents having the desired detergency properties for incorporation into commercial granular detergent products, such as laundry powders and tablets are thick, viscous, sticky liquids or semi-solid or waxy materials. The presence of these materials in a detergent slurry (crutcher mix) prior to spray drying in amounts greater than about 2-3 percent by weight is impractical since the nonionic synthetic detergent will "plume" during spray drying and a significant portion can be lost through the gaseous exhaust of the spray drying tower.
The art has recognized the application of nonionic synthetic detergents of this type to various particulate carrier bases to produce relatively free flowing granular materials that can be used as household laundry products. Representative patents containing teachings and disclosures of methods for producing granular free flowing laundry detergents by post spraying a nonionic synthetic organic detergent onto a spray dried particulate product containing detergent builders include: among others: Di Salvo et al U.S. Pat. Nos. 3,849,327 and 3,888,098; Gabler et al U.S. Pat. No. 3,538,004; Kingry U.S. Pat. No. 3,888,781; and British Pat. No. 918,499 (Feb. 13, 1963). The prior art in this regard is typified by post spraying from about 1 to a maximum of 10 percent by weight of a nonionic synthetic detergent onto a spray dried bead that contains a substantial proportion of a surface active agent such as anionic detergents, filler materials, and detergent builders.
Further, certain desirable ingredients for detergent formulations such as cationic surface active agents that provide fabric softening properties and optical brighteners, bluing agents and enzymatic materials cannot be spray dried because of thermal composition. Such materials can be incorporated into a granular detergent according to the invention by post spraying them onto the spray dried base builder beads either alone or in addition to a nonionic detergent or other suitable ingredients.
Detergent formulations in the form of cleaning tablets are known in the art, i.e., for example see U.S. Pat. Nos. 2,875,155; 3,034,911; 3,081,267, 3,247,122; 3,247,123; 3,370,015; 3,417,024 and 3,503,889 and many others.
For a cleaning tablet to be commercially acceptable, it must be of sufficient strength so that it will not break under normal production, packaging and handling conditions, yet it must also be readily dispersed in cold water so as to provide the desired function comparable to that of the granular or liquid products, which are, because of their physical nature, readily dispersable in the washing medium. A disintergration time for a detergent tablet of about three minutes or less is considered to be a highly desirable rate from both the viewpoint of amount of cleaning, which is a function of the rate of the detergent being dispersed in the water, and the minimization of spotting of the clothes, which might be caused by local concentrations of detergent, e.g., large pieces of the tablet being trapped in the clothes. Additionally, overcoming these problems is further complicated by the need today for cleaning products which are equally suitable for both hot water and cold water applications. Cold water washing, in particular, is especially important because of the need to conserve energy and it is important that the tablets may be used interchangeably for either cleaning application. Cold water, in terms of cleaning products, usually means tap water, which has a temperature range of about 70.degree. F.
The art has attempted to resolve the dichotomy between a cleaning tablet having sufficient physical strength and satisfactory water-dispersability, as well as other associated problems normally encountered with such tablet products, by using a very specialized cleaning formulations and processing techniques. The solution to these problems is beset with many difficulties however. Handling of the tablet without breakage normally requires the tablet to have a high strength; but, cleaning tablets normally disintegrate much more slowly as the tablet strength is increased. These competing forces, coupled with the inherent nature of cleaning tablets to be much more readily disintegrated in hot water than in cold water, presents the manufacturer with formidable problems to be overcome to provide tablets having the desired characteristics.
Further, the operation of a conventional tablet press is hampered drastically if the base powder beads to be compressed into tablet form are (a) not free flowing (b) sticky and tacky (c) light in density with correspondingly high bulk and (d) weak and fragile when compressed.
A primary advantage of the invention is to provide base detergent beads that are free flowing so as not to impede the tablet press and can be readily formed into cleaning tablets of improved physical integrity and disintegration rate in the washing medium.